I did some testing with triggers a Merge statement today and it appears that in statement level triggers the INSERTING, UPDATING keywords do not work when executing the MERGE statement. Perhaps another reason NOT to use triggers for your very nicely written aricle on triggers.

Well, that is appropriate really, because a merge is neither an insert or an update really. For example, if the merge finds nothing to update, only inserts, it would have been wrong to fire the before statement in the context of inserting, and vice versa. Remember, the before statement, is exactly that. Before the statement.